Plastic closing device comprising a cutting collar

ABSTRACT

The invention relates to a plastic closing device comprising a pouring part ( 1 ) for fixing onto packaging, a screw cap ( 2 ) that can be screwed onto the pouring part ( 1 ) and a self-opening collar ( 3 ) in the pouring part ( 1 ) that can be moved downwards with a screw action onto the packaging in order to open the latter. The screw cap ( 2 ) has a follower ( 24 ), which acts on a stop element ( 36 ) of the self-opening collar ( 3 ) and which, when the screw cap ( 2 ) is first opened, moves the self-opening collar ( 3 ) inside the pouring part ( 1 ) into a lower position onto the packaging in order to open the latter. When the pouring part ( 1 ) is subsequently closed by the screw cap ( 2 ), the self-opening collar ( 3 ) remains in the lower position. The self-opening collar has several cutting and/or piercing elements ( 32   a   , 32   b ) with a substantially quadrangular basic form. Said form is interrupted by a lower longitudinal edge comprising a sloping and a longer and flatter rising region. Said form makes the closing device suitable for various types of packaging.

TECHNICAL FIELD

The invention relates to a plastic closing device comprising a cutting collar according to the preamble of patent claim 1. The closing device is in particular suitable for sealed packages, which contain a free-flowing content, preferably a beverage.

STATE OF THE ART

A generic closing device is known from EP 1 088 764. This closing device consists of three parts, namely a screw cap, a bottom part and a cutting collar. The bottom part is embodied in a tubular manner and encompasses at its bottom side a circumferential flange, by means of which it can be fixed onto a drink carton. The tubular part forms a pouring spout, which can be closed by means of the screw cap. The cutting collar is also embodied in a tubular manner and encompasses a cutting tooth at its lower end. In the unopened state of the packaging, the cutting collar is located within the bottom part, and the screw cap is screwed onto the bottom part. In the event that the screw cap is now rotated in order to open the closing device, the cutting collar rotates as well, thanks to a follower system, with the cutting collar, thereby simultaneously moving downwards in axial direction. The packaging and in particular the film of the packaging is thereby cut open in a circular manner along a predetermined breaking line. The follower contact between screw cap and cutting collar is disconnected after a predetermined rotation angle, that is, when the packaging is opened to a sufficient extent. Thereafter, the screw cap can be completely removed from the pouring spout and can be placed thereon again, as necessary, so as to perform a closing action, without once again moving the cutting collar, which projects into the packaging. The cutting collar and the bottom part are molded in one piece in a pre-assembly group configuration, in which they are secured coaxially to one another by means of radial connecting bridges. These bridges extend between the top edge of the cutting collar and the bottom side of the bottom part. These bridges are broken when the cutting collar is pushed into the bottom part for the first time.

Theoretically, there is no limit to the form and design of such closures. In practice, however, they must be capable of being produced in a injection molding process. They should furthermore be capable of being produced as cost-efficiently as possible.

Different types of packaging are known, which can be opened by means of such self-opening closures. Among the known packaging, there is, in particular, composite packaging, which comprises a layer of paper or cardboard, which is laminated with one or a plurality of thin plastic and/or metal layers. A typical composite packaging comprises, e.g., a cardboard layer, which is provided towards the inside of the packaging with a thin layer of aluminum, which, in turn, is provided with a layer of polyethylene (PE). Lately, packaging which no longer encompasses a cardboard layer, but which is instead formed from a relatively thick plastic film, in particular pure PE packaging, which is, at most, provided with one or a plurality of very thin barrier layers, is also becoming accepted.

In the production of the packaging, the packaging is typically weakened, e.g. pre-punched, in the region in which the closure is later attached so as to make it possible for the cutting collar to more easily penetrate the packaging wall. Dependent on the design of the packaging and on the production method, there are different possibilities for this. In a pure PE packaging, a circular weakening line can, e.g., be embodied in the wall having a lower wall thickness. In a composite packaging, a weakening region is typically formed in that the cardboard layer is penetrated (e.g. pre-punched) as completely as possible in a circular curve-shaped region. In the event that this pre-punching takes place before the cardboard is coated with the further layers, the circular disk, which is cut out of the cardboard, usually is removed prior to the coating with the further layers, thus creating a packaging, which, in the region of the subsequent opening, encompasses a circular region, which only consists of the thin film layers of aluminum and/or plastic, but which does not contain cardboard. However, in the event that the cardboard layer is perforated only after the coating, the cut-out circular disk remains connected to the film layers.

Typically, a different type of self-opening collar is used for each of this differently designed packaging. In particular, e.g. for a composite packaging having a circular region in the region of the opening that only consists of film layers, it is disadvantageous if the self-opening collar exerts a high axial force onto the film layers (“pressing”). In this case, there is a tendency for the film layers to avoid this force by bulging towards the interior of the packaging. Instead, such a packaging should be torn open by means of cutting, if possible. Vice versa, it is advantageous for packaging in which the cardboard disk is still present if mainly a pressing force is exerted.

Known self-opening closures furthermore require a very accurate positioning of the closure on the opening region as provided and prepared by means of a weakening. In the event that the positioning for such closures takes place so as not to be accurately centered, a clean opening of the packaging is often not ensured.

A closure comprising a self-opening collar is known from WO 03/002419, which encompasses two cutting elements, which are arranged so as to follow one another and which have a triangular basic form.

WO 2006/089440 also shows a self-opening collar comprising two triangular cutting teeth.

WO 2004/083055 also discloses triangular cutting teeth. Additionally, a perforating tooth is present herein. In the event that the cutting teeth did not cleanly cut through a film of the laminated packaging material, it is pierced by the perforating tooth.

WO 2007/030965 discloses a self-opening collar comprising three teeth. Each of these teeth has a triangular basic form, which is followed by a reinforcement shoulder. For two teeth, this shoulder is formed so as to follow the tooth in the direction of rotation, while for the third tooth it is formed so as to lead that tooth.

Each of these self-opening collars is optimized for a certain type of packaging. None of the self-opening closures thus delivers a satisfactory result for all of the afore-mentioned types of packaging, but will fail for at least one type of packaging.

DESCRIPTION OF THE INVENTION

It is thus an object of the invention to create a closing device of the afore-mentioned type that can be produced in a cost-efficient manner. It is a further object of the invention to provide a closing device that is suitable to efficiently pierce different types of differently designed or differently prepared packaging. It is a further object of the invention to specify a closing device that opens different types of packaging in a satisfactory manner even in the event that it is not perfectly centered on a weakening region of the packaging.

A closing device comprising the features of patent claim 1 solves these objects.

The plastic closing device according to the invention encompasses a pouring part for fixing onto packaging, a screw cap, which is adapted to be screwed onto the pouring part, and a self-opening collar in the pouring part, which is adapted to be moved downwards towards the packaging with a screw action in order to open the packaging. The screw cap has at least one drive element or driver, which acts on at least one stop element of the self-opening collar and which, when the screw cap is first opened, causes the self-opening collar within the pouring part to move into a lower position towards the packaging in order to open the latter. When the pouring part is subsequently closed by the screw cap, the self-opening collar remains in its lower position. The self-opening collar comprises at least two cutting and/or piercing elements, which project downwards, which are arranged along the periphery of the self-opening collar and which form a lower edge thereof. These cutting and/or piercing elements have a substantially rectangular form. A longitudinal edge, which is relatively long with respect to the direction of rotation and which projects downwards, interrupts the rectangular form and forms a triangle, which projects downwards, thus creating a tip, which projects downwards. With reference to the direction of rotation of the collar, the longitudinal edge has at its front a portion that slopes or declines downwards and that subsequently rises again, wherein the rising portion is made so as to be longer and flatter than the declining portion and runs inclined at a flat angle relative to a plane that is perpendicular to the longitudinal axis.

This design of the cutting and/or piercing elements represents the result of an optimization with reference to fundamentally contradicting demands. It turned out that a particularly easy and clean opening of the packaging is attained by means of the proposed form, namely similarly easy for different types of packaging (in particular laminated cardboard packaging comprising different types of weakening as well as PE film packaging). The leading portion of the longitudinal edge thus substantially has a cutting effect in response to the rotation of the collar, while the entire longitudinal edge, including the rear portion, also additionally has a pushing effect in response to the downwards movement.

The rising and/or declining portion can be straight or can be curved. Preferably, it is considerably longer than the rising portion and preferably has a length, which is at least 2.5 times the length of the rising portion. Preferably, the rising portion opens an angle of at least 40°, particularly preferred approx. 50° to the horizontal (thus to a plane, which is perpendicular to the axis of rotation), all-over, while the angle of the declining portion to the horizontal is preferably less than 30°, particularly preferably less than 20°,all-over. An obtuse angle, that is, an angle of more than 90 degrees, is embodied at the location between the rising portion and the declining portion of the longitudinal edge.

Preferably, the longitudinal edge projecting downwards forms, at least in its rising portion, a cutting edge, that is, the self-opening collar is embodied in this region so as to taper in a blade-like manner towards the longitudinal edge. The tearing of the packaging is thus facilitated. Preferably, a cutting edge is also provided in the declining portion. Film material, e.g., which stretches elastically across the longitudinal edge, can thus also be torn efficiently in this region.

Preferably, the cutting edge is provided on an inner peripheral surface of the self-opening collar. In other words, the self-opening collar preferably tapers towards the longitudinal edge only at its outer periphery in order to thus form the cutting edge, while the inner circumference in the region of the longitudinal edge is constant. The cut material is thus displaced outwards, which adds to a clean cross section of the cut-out material disk of the packaging.

Preferably, all of the cutting and/or piercing elements project downwards to the same extent. They thus contact the weakening region of the packaging at the same time and perforate said packaging at a plurality of locations at the same time. Even in the event that the perforation should not succeed at a location, an easy opening is ensured. Furthermore, a relatively large, even pressure is thus exerted onto the weakening region, which is particularly advantageous for certain types of packaging.

In order to attain the most even force distribution, the cutting and/or piercing elements (32 a-32 e) are preferably arranged along the periphery so as to be distributed at the same distance.

Additionally, the self-opening collar can encompass at least one hold-down element which forms the lower edge together with the cutting and/or piercing elements and which serves the purpose of pressing the detached material disk of the packaging downwards in order to prevent that said material disk hinders the pouring. The hold-down element is then arranged so as to follow the cutting and/or piercing elements in the direction of rotation.

In this case, the cutting and/or piercing elements are preferably arranged so as to be distributed successively and at the same distance along the periphery, and the distance from the hold-down element to the first cutting and/or piercing element in the direction of rotation is preferably greater than the distance of the cutting and/or piercing elements among one another.

In the event that a hold-down element is available, the self-opening collar preferably comprises three to five, in particular four cutting and/or piercing elements. Without hold-down element, it is advantageous when the self-opening collar encompasses four to six, in particular five cutting and/or piercing elements. With a smaller number, the force distribution is less even and the material thickness of each individual cutting and/or piercing element must be increased considerably, which increases the production price. A larger number of such elements, in turn, has the effect that each individual element becomes smaller, which is also disadvantageous in view of the stability. With a number of elements that is too large, the pressing force exerted by each individual element furthermore becomes too small and it is no longer possible to attain a clean cutting effect. In essence, the optimal number is the result of a drawn-out optimization in view of the different and partly contradictory demands that must be fulfilled by the self-opening collar in order to render it suitable for different types of packaging.

For guiding purposes, the self-opening collar preferably has an external thread, which cogs with an internal thread of the pouring part so that the self-opening collar rotates during its downwards movement. The pitch of the external thread is preferably chosen in such a manner that the self-opening collar performs a rotation of less than 360 degrees, in particular 300 degrees, in response to the unscrewing of the screw cap.

Preferably, only a single drive element is provided on the screw cap. Preferably, only a single stop element is accordingly provided on the self-opening collar as well. Preferably, this stop element is located in the vicinity of a cutting and/or piercing element that is foremost in the direction of rotation of the collar. However, a plurality of stop elements, which are arranged so as to be distributed along the periphery, can also be available, wherein the driver only engages with one of them.

In the case of a single drive element or driver, the closing device is designed in a very simple manner. This minimizes the production costs. Material can, in particular, be saved for the closure, because the driver system is reduced to an absolute minimum. Thanks to the simple form of the closing device, its production is also simplified and the waste of closures not conforming to quality is relatively low.

Preferably, the driver has a driver edge, which runs in axial direction. The driver edge then preferably encompasses a stop surface, which slopes relative to the radial direction. In particular, the driver can be embodied in a tooth-shaped manner with the perpendicularly running driver edge and a back edge comprising an angle of slope of maximally 45°. Preferably, the driver has a height corresponding approximately to the height of the pouring part. The stop element can be a lug projecting from an inner wall of the self-opening collar, which comprises an edge running in axial direction and which extends only across a part of the height of the self-opening collar. The lug can then have a undercut relative to the radial direction.

Further advantageous embodiments become evident from the dependent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject-matter of the invention will be exemplified below by means of preferred embodiments, which are illustrated in the enclosed drawings.

FIG. 1 shows a longitudinal section through a closing device according to a first embodiment in a state prior to its first use;

FIG. 2 shows the device according to FIG. 1 in response to the screw cap having been unscrewed;

FIG. 3 shows a side view of the device according to FIG. 2;

FIG. 4 shows a view of the closure according to FIG. 2 from below, mounted onto a packaging;

FIG. 5 shows a longitudinal section through the pouring part and the self-opening collar of the device according to FIG. 1 after its production;

FIG. 6 shows a perspective illustration of the device according to FIG. 1 from below;

FIG. 7 shows a perspective illustration of the device according to FIG. 1 from the side;

FIG. 8 shows a view of the device according to FIG. 1 from below;

FIG. 9 shows a side view of the pouring part and of the self-opening collar according to FIG. 1;

FIG. 10 shows a section through A-A according to FIG. 9;

FIG. 11 shows a longitudinal section through a closure according to the invention according to a second embodiment;

FIG. 12 shows a perspective illustration of the closure according to FIG. 11 and

FIG. 13 shows a view of the closure according to FIG. 11 from below, mounted onto a packaging.

WAYS OF CARRYING OUT THE INVENTION

FIGS. 1 to 10 illustrate an exemplary embodiment of a closing device or of a self-opening closure. Such closures are fixed onto packaging with free-flowing content, in particular onto drink cartons made of cardboard comprising a film on the inside thereof. In this region, the packaging preferably already encompasses a pouring opening, which is predefined, but which is still closed in an airtight manner. Preferably, the cardboard is already perforated or otherwise weakened, but the film arranged therebelow is still intact.

The device is made of plastic in a injection molding process, wherein the individual parts can be manufactured from the same or from a different plastic.

As can be seen in FIG. 1, the device substantially comprises a pouring part 1, a screw cap 2 and a self-opening collar 3. Preferably, a tamper-proof strip 4 is additionally available, which is preferably produced in one piece with the screw cap 2. Pouring part 1 and self-opening collar 3 are preferably also produced together in one piece. However, it is also possible to manufacture them separately from one another.

The pouring part 1 substantially consists of a tube-shaped pouring spout 10 having a continuous pouring opening and a flange 13, which extends outwards from the pouring spout 10 and which is integrally molded on a lower end of the pouring spout 10. This flange 13 is welded onto the packaging or is otherwise fixed thereon so that the pouring spout 10 comes to rest above the predefined pouring opening of the packaging.

The pouring spout 10 encompasses an external thread 12 and an internal thread 14. As is described further below, bars 15 comprising projecting, undercut retaining lugs 15′ are arranged in the lower region of the pouring spout 10 above the flange 13.

The screw cap 2 preferably has a cylindrical jacket wall 21 and an approximately flat top surface 20. The cap 2 can be screwed onto the external thread 12 of the pouring part 1 by means of an internal thread 22. The jacket wall 21 is connected to the tamper-proof strip 4 via predetermined breaking points 23.

A circumferential sealing lip 26, which in the closed state of the cap 2 abuts on the inner side of the pouring spout 10 in a resilient manner, preferably projects downwards in the inner region of the cap 2.

The cap 2 encompasses a single driver 24, which projects inwards or downwards, respectively, and which is preferably integrally molded onto the inner side of the top surface 20. Preferably, the driver 24 has a triangular basic form, wherein it is curved along a circle that is concentric to the internal thread 14. A driver edge 14 runs in axial direction, wherein it preferably has a stop surface that slopes towards the radial direction, thus forming a rear-engaging element. A back follows the driver edge in the opening direction of rotation of the cap 2, wherein the back has an angle of inclination of maximally 45°. The height of the driver 24 corresponds approximately to the height of the pouring part 1, in particular of the pouring spout 10.

The self-opening collar 3 has a hollow-cylindrical form and has a continuous opening. It substantially consists of a ring 30 comprising an external thread 31 and of cutting and/or piercing elements 32 a-32 e, which protrude from the ring 30 downwards in approximately perpendicular direction. These cutting and/or piercing elements 32 a-32 e are distributed along the periphery of the self-opening collar 3 and are arranged at a distance 33 to one another and form a lower edge thereof. Furthermore, at least another down-hold element 35 can be available at this edge. These elements will be described in more detail below.

The collar 3 encompasses at least one, preferably exactly one stop element 36, as can be seen in FIG. 2. The stop element 36 is a lug projecting from an inner wall of the self-opening collar 3, which encompasses an edge running in axial direction and which preferably extends only across a part of the height of the self-opening collar 3. Preferably, the lug encompasses a stop surface that is inclined relative to the radial direction. The lug preferably extends in the region of the external thread 31, wherein the external thread extends along a greater height than the lug. The stop element 36 is preferably arranged in the direction of rotation of the collar 3 in the region of the first cutting and/or piercing element 32 a, wherein it can be arranged in the front or rear portion thereof or therebetween.

In FIG. 1, the cap 2 is screwed onto the pouring part 1 and the self-opening collar 3 is located in the pouring spout 10, wherein it does not project downwards beyond said pouring spout 10 or the flange 13, respectively. The tamper-proof strip 4 is intact. This is the situation as it is at hand prior to the first use of the closure. In this position, the closure can be mounted onto the packaging.

In the event that the cap 2 is unscrewed, the driver 24 abuts to the stop element 36. This can be seen in FIG. 6. In the event that the surfaces thereof are embodied so as to be inclined, at least a partial form closure takes place moreover, which reinforces the connection between cap 2 and collar 3.

The external thread 31 of the collar 3 cogs with the internal thread 14 of the pouring part 1 so that the collar 3 rotates downwards with a screw action within the pouring spout 10 when the cap 2 is first unscrewed. When the cap 2 is removed, the engagement between driver 24 and stop element 36 is disconnected.

In FIG. 2, the cap 2 is removed, the predetermined breaking points 23 to the tamper-proof strip 4 are broken and the collar 3 has moved downwards so that the cap 2 is now held in the lower region of the pouring spout 10 only with its upper part, but projects downwards beyond the flange 13 with its teeth 32 a-32 e. This is the situation as it is at hand after the first-time opening of the closure.

This general situation is once again illustrated in FIG. 4, wherein it can be seen that a section D, which predefines the pouring opening of the packaging K, is not completely detached, but remains fixed thereon via a small partial circle. Said section D, however, is held in an open position by at least one of the cutting and/or piercing elements 32 e.

The collar 3 now remains in this lower position, even in the event that the cap 2 is attached again and screwed tightly.

As can now be seen in FIG. 3, this embodiment encompasses a total of five cutting and/or piercing elements 32 a-32 e. These are preferably made to have the same height. These elements are arranged so as to be distributed across the periphery of the collar 3 at the same distance.

Preferably, they are formed to be identical and to have the same height. They have a substantially rectangular form, wherein a longitudinal edge projecting downwards interrupts the rectangular form in each case. The edge is inclined, wherein the height of the element in the direction of rotation of the collar 3 decreases rearwards. The longitudinal edge is relatively long so that it is greater than the distances 33 between the elements. Preferably, it is at least twice as long as the distance 33 located therebetween.

In this example, the longitudinal edge is embodied so as to be relatively blunt so that the elements rather or exclusively act as pushers or piercers and not as cutting elements.

However, as is illustrated in FIGS. 11 to 13, they can also be designed as cutting elements, without having to considerably change their basic form. In the further preferred exemplary embodiment illustrated herein, a longitudinal edge that initially declines or slopes downwards in the direction of rotation of the sleeve 3 and which subsequently rises is formed instead of the longitudinal edge according to FIG. 3, which runs straight, so that a tip is formed that projects downwards. The rising portion is thereby embodied so as to be longer and flatter than the declining portion, which acts as cutting edge. In the instant example, the length of the rising portion is approximately three times the length of the declining portion. The declining portion subtends an angle of approx. 50° to the horizontal (that is, to the plane that stands perpendicularly on the direction of rotation), while the rising portion forms an angle of only approx. 12° to the horizontal. An obtuse angle, which here is approx. 118°, is formed between the rising and the declining portions. The declining as well as the rising portions are designed in a blade-like manner as a cutting edge. For this, the self-opening collar tapers towards the cutting edge or approaches the cutting edge in a blade-like manner, respectively. In the instant case, this tapering takes place only at the outer side of the self-opening collar. The inner jacket surface of the self-opening collar, however, is cylindrical in the region of the cutting edge. Through this, the cutting edge displaces the cut material outwards in response to the cutting and thus contributes to a clean cross-section, on the one hand.

In the example of FIGS. 11 to 13, a total of four cutting and/or piercing elements 32 a-32 d are provided, which are followed by a single hold-down element 35. All of the cutting elements 32 are designed to have the same size and the same form. The hold-down element 35 also has approximately the same width and length, respectively, but does not have a cutting tip and is thus smaller. The distance from the hold-down element 35 to the first cutting and/or piercing tooth 32 in the direction of rotation is greater than the distance of the teeth 32 among one another.

An advantage of these two embodiments is that they need no longer be accurately positioned on the predefined pouring opening. Thanks to their cutting and/or piercing elements, which are relatively long or wide in the direction of rotation of the collar 3, they can also contact the section at a distance to the perforation and can still exert a sufficient amount of pressure in order to disconnect the section D from the packaging. Furthermore, a relatively steep thread can be chosen between collar 3 and pouring spout 10 thanks to these elements so that a rotation of less than 360°, in particular of less than 300°, is sufficient to open the closure and to push down the section D.

FIG. 5 illustrates a possibility for producing such a closure. The cap is molded separately, the collar 3 and the pouring part 2, however, are produced in one piece. The collar 3 thereby projects partially beyond the pouring spout 2 on top, wherein it is connected to the pouring part 2 via connecting bridges 5. After the part has been molded, the collar 3 is pressed completely into the pouring spout 10, wherein the connecting bridges 5 break.

FIGS. 7 to 10 illustrate a preferred embodiment of a first opening identification. This type of identification can be used not only for this closure but for all closures that comprise a pouring spout having a flange and a cap that can be screwed onto the spout.

Starting at the pouring spout 10, a plurality of bars 15, which run parallel to a tangent at the pouring spout 10 and parallel to one another, are integrally molded on the upper side of the flange 13. Preferably, their free ends are located on a common circle, which runs concentrically to the outer periphery of the pouring spout 10. One bar 15 or a plurality of bars 15, here two, can also run perpendicular to the remaining bars 15. This can be seen in FIG. 10. The free ends form undercut retaining lugs 15′, as can be seen in FIG. 9.

As is illustrated in FIG. 7, the tamper-proof strip 4 is injection molded at the cap 2 via predetermined breaking bridges 23, wherein said tamper-proof strip 4 preferably completely rotates around the cap 2. In the state in which the closure has never been opened, the retaining bars 40 of the tamper-proof strip 4 engage with the retaining lugs 15′ and prevent a mutual rotation of cap 2 and pouring part 1, as can be seen in FIG. 10. In response to a rotation of the cap 2, the predetermined breaking bridges 23 are disconnected by axial drag and the tamper-proof strip is completely disconnected from the cap 2.

Preferably, connecting bridges 6, which are preferably wider than the bars 23, are still available between cap 2 and tamper-proof strip 4. Preferably, they are arranged evenly along the periphery of the cap, as can be seen in FIG. 8, for example. In the example illustrated herein, three such bridges 6 are available, but their number can vary. These bridges facilitate and shorten the injection molding process, because a relatively large amount of material can be transported via these bridges. These bridges 6 are broken after the production of the cap and preferably prior to the mounting of the closure. Preferably, they are cut through by means of a knife or a laser beam. Such connecting bridges can be used for all embodiments. They can furthermore be used for all individual components, which are injection molded together. This production method is not limited to the closures according to the invention as described herein.

Additional forms of the self-opening collar 3, in particular of the cutting and piercing elements, are possible. The number of teeth can also be varied. Furthermore, the above-mentioned external and internal threads can be continuous or only partial threads.

LIST OF REFERENCE NUMERALS

-   1 pouring part -   10 pouring spout -   12 external thread -   13 flange -   14 internal thread -   15 bar -   15′ retaining lug -   2 screw cap -   20 top surface -   21 jacket wall -   22 internal thread -   23 predetermined breaking points -   24 driver -   26 sealing lip -   3 self-opening collar -   30 ring -   31 external thread -   32 a first piercing element -   32 b to -   32 e second to fifth piercing element -   33 distance -   34 second cutting tooth -   35 hold-down tooth -   36 stop element -   4 tamper-proof strip -   40 retaining bar -   5 connecting bar -   6 connecting bridge -   K cardboard packaging -   D section 

1. A plastic closing device comprising a pouring part for fixing onto a packaging, a screw caps adapted to be screwed onto the pouring part, and a self-opening collar adapted to be moved downwards in the pouring part towards the packaging with a screw action for opening the packaging, wherein the screw cap comprises at least one driver, which acts on at least one stop element of the self-opening collar and which causes the self-opening collar to move within the pouring part into a lower position towards the packaging in order to open said packaging when the screw cap is first opened, and which causes the self-opening collar to remain in its lower position when the pouring part is subsequently closed by means of the screw cap, and wherein the self-opening collar comprises at least two downwards-projecting cutting or piercing elements arranged along a periphery of the self-opening collar and forming a lower edge thereof, wherein the cutting or piercing elements have a substantially rectangular form, wherein a downwardly projecting longitudinal edge interrupts the rectangular form and forms a downwardly projecting triangle, thus creating a downwardly projecting tip, wherein the longitudinal edge has, at its front relative to the direction of rotation of the collar, a portion that declines downwards and a portion which subsequently rises again, and wherein the rising portion is longer and flatter than the declining portion.
 2. The closing device according to claim 1, wherein the rising portion of the longitudinal edge has a length that is at least 2.5 times the length of the declining portion.
 3. The closing device according to claim 1, wherein an obtuse angle is present between the rising portion and the declining portion of the longitudinal edge.
 4. The closing device according to claim 1, wherein the downwardly projecting longitudinal edge forms a cutting edge at least in its declining portion.
 5. The closing device according to claim 4, wherein the downwardly projecting longitudinal edge forms a cutting edge in its declining portion as well as in its rising portion.
 6. The closing device according to claim 4, wherein the cutting edge is provided on an inner peripheral surface of the self-opening collar.
 7. The closing device according to claim 1, wherein the cutting or piercing elements project downwards to the same extent.
 8. The closing device according to claim 1, wherein the cutting or piercing elements are arranged along the periphery so as to be distributed at the same distance.
 9. The closing device according to claim 1, wherein the self-opening collar comprises four to six cutting or piercing elements.
 10. The closing device according to claim 1, wherein the self-opening collar comprises at least one hold-down element, which forms the lower edge together with the cutting or piercing elements.
 11. The closing device according to claim 10, wherein the self-opening collar comprises three to five cutting or piercing elements and one hold-down element.
 12. The closing device according to claim 1, wherein the self-opening collar comprises an external thread, and wherein the pouring part comprises an internal thread that cogs with said external thread, so that the self-opening collar rotates when being moved downward.
 13. The closing device according to claim 12, wherein the external thread has a pitch, which is chosen in such a manner that the self-opening collar performs a rotation of less than 360 degrees, in response to the unscrewing of the screw cap.
 14. The closing device according to claim 1, comprising a single driver.
 15. The closing device according to claim 1, comprising a tamper-proof strip having first bars, the tamper-proof strip being connected to the cap and surrounding said cap at least partially, wherein second bars comprising projecting lugs, which run parallel to a tangent of a pouring spout are provided on a flange of the pouring part, and wherein the bars of the tamper-proof strip engage the bars of the pouring part.
 16. (canceled)
 17. (canceled) 